Screen printing is a printing method for printing a target printing pattern by pushing out a printing material such as ink or paste by a sliding operation of a squeegee through an opening portion on a screen printing plate and transferring the shape of the opening portion to the matter to be printed.
There are many types of screen printing plates used in the screen printing according to differences in the materials or manufacturing methods. Among them, those with an opening portion formed for printing with an emulsion on a screen fabric in which a thin metallic wire is woven or those with an opening portion formed for printing with etching or laser machining on a thin metal plate are generally used.
The screen printing has high productivity and is utilized in many industrial fields.
However, when a target printing pattern, particularly a fine design is to be printed using the screen printing, there is a problem that transfer performance is lowered by bleeding of a printing material from an opening end portion. In the meantime, particularly high transfer performance is in demand in the screen printing used in the electronics industry field.
For example, if a printing operation is carried out using a screen printing plate la with a straight opening end portion 3a in an opening portion 2a as shown in FIG. 3, a printing pattern 5a after printing, which is the shape of the end portion of the printing material, does not match a target printing pattern 4a due to bleeding of the printing material and does not become straight. Even though the opening end portion 3a is made straight essentially in order to make the end portion of the printing material straight, a printing area is expanded and the end portion of the printing material becomes irregular due to the bleeding of the printing material.
There can be various causes in complex for this bleeding phenomenon, but particularly, (1) high printing pressure, (2) surface shape of the matter to be printed, (3) mesh intersection, and (4) viscosity of the printing material can be cited.
One of methods to prevent such bleeding of the printing material is to provide a printing-material reservoir in a recess-shaped groove in the vicinity of an opening portion on the side in contact with a matter to be printed of a screen printing plate (See Japanese Patent Laid-Open No. 10-329444, for example).
Other methods of preventing bleeding include a method to provide a bank in the normal direction of a contact face with a matter to be printed at a given height along the opening end portion on the side in contact with the matter to be printed of a screen printing plate (See Japanese Patent Laid-Open No. 5-270161, for example).
However, with these methods, the manufacturing method of a screen printing plate becomes complicated and its manufacturing cost is increased, which is a problem.
The surface shape of the matter to be printed largely affects the bleeding phenomenon. For example, in a solar cell in which an electrode is produced by screen printing with a conductive paste, the surface shape of a matter to be printed (substrate) is a collection of a pyramid called as a texture, and the printing plate is not necessarily brought into close contact with the surface of the matter to be printed but a gap is generated. In that case, the above methods are not effective.